The present invention relates to an automatic sewing machine in which a cloth presser unit holding a material to be sewed is moved according a predetermined pattern thereby to form a seam having a predetermined pattern, and more particularly to a control device for controlling the speed of rotation of the automatic sewing machine and the movement of the cloth presser unit.
FIG. 14 shows an external appearance of a conventional ordinary automatic sewing machine. The automatic sewing machine comprises: a sewing machine mechanism section 25 provided on a sewing machine table 201, the sewing machine mechanism section 25 incorporating a mechanism for forming seams on a material to be sewed with a needle bar 202; an electric motor 203 for driving the sewing machine mechanism section 25; a cloth presser unit 206 for holding a material to be sewed (hereinafter referred to as "a sewing material," when applicable) between an upper presser plate 204 and a lower presser plate 205 by using an air pressure; and a biaxial drive mechanism 208 for horizontally moving the cloth presser unit 206 on a shuttle race slide 207. A control device 224 for controlling the operations of the above-described components is provided, in the form of two upper and lower layers, in one side portion of the table 201. The upper portion of the control device comprises: an operating panel 40 including a variety of switches for specifying a desired operation for the automatic sewing machine; and a data reading unit for reading data on the patterns of movement of the biaxial drive mechanism 208 from a data storing medium (not shown) which is detachably mounted therein, to control the timing of the operations of the whole sewing machine and the movement of the biaxial drive mechanism 208.
The operating panel 40 has a power switch 211, a reset switch 222 for positioning the biaxial drive mechanism 208 in place to reset the system; and a test switch for driving the two axes according to a given sewing data with the needle maintained stopped.
A foot pedal 31 shown in the lower portion of FIG. 14 includes: a start switch 217 for providing a sewing start instruction; and a switch 214 for activating the cloth presser unit 206 (hereinafter referred to as "a cloth presser switch 204," when applicable). The sewing machine mechanism section 25 has a stop switch 215 for suspending a sewing operation. The sewing machine further comprises: origin detecting units 29 and 30 provided for the biaxial drive mechanism 208 to detect the mechanical origins of the two axes.
Further in FIG. 14, reference numeral 40 designates the aforementioned operating panel for specifying a sewing pattern and a sewing speed; 220, a liquid crystal display unit for displaying operating procedures, current sewing conditions, and error messages (hereinafter referred to as "an LCD 220," when applicable); 222, a reset switch for resetting a positioning system at a predetermined position; 223, a group of switches including digital keys for setting sewing patterns, the aforementioned reset switch 222, and a speed setting switch 221; 47, a magnetic data writing and reading unit for writing data in a floppy disk (hereinafter referred merely to as "an FD," when applicable) and reading data therefrom (hereinafter referred to as "an FDD 47," when applicable); and 224, the aforementioned control device for controlling the operations of the automatic sewing machine.
The arrangement of the control device 224 will be described with reference to FIG. 20.
In FIG. 20, reference numeral 1 designates a microcomputer including a CPU and a direct memory access (hereinafter referred to as "a DMA," when applicable) for making access to memory directly without the aid of an external interruption controller or the CPU; 32, a crystal oscillator for producing a fundamental frequency to operate the microcomputer; 2, a memory address latch circuit (for instance 74LS373) for latching an address in a memory (RAM 61 and ROM 7); 3, a memory data buffer (for instance 74LS245) for transferring data from the memory (ROM 7 and RAM 61) to the microcomputer or vice versa; 4, a peripheral data buffer (for instance 74LS245) for transferring data from the microcomputer 1 to peripheral elements other than the memory or vice versa; 5, an IC selection signal generating circuit (hereinafter referred to as "a decoder 5," when applicable) for producing IC selection signals to select the memory (ROM 7 and RAM 61) and the periphery elements, respectively; 61, a data writing and reading memory element (hereinafter referred to as "a RAM," when applicable); 7, a non-volatile read-only memory element (hereinafter referred to as "a ROM," when applicable); and 33, a power source backup circuit which provides its output power normally for several days to eliminate the difficulty that, in the case where a RAM is employed as a data writing and reading memory element, all the contents of the RAM are erased when the power switch is turned off because the RAM is a volatile memory element.
Further in FIG. 20, reference numeral 43 designates a frequency divider circuit for frequency-dividing the signal having a predetermined frequency outputted by the microcomputer 1, the output of the frequency divider circuit being applied to a serial communication element 34 and a keyboard controller 37; 34, the aforementioned serial communication element (for instance 8251) connected to the peripheral data buffer for converting parallel data to serial data or serial data into parallel data; 60, a driver for modifying the output data of the serial communication element 34 in accordance with a communication standard (for instance RS-232C or RS-422) (hereinafter referred to as "a serial communication driver 60," when applicable), the serial communication drive 60 having an input element and an output element; and 36, a unit which receives an input signal when the serial communication drive 60 provides an output signal, and which provides an output signal when the serial communication driver 60 receives an input signal. That is, the unit 36 is a party for serial communication, and it is for instance a personal computer (hereinafter referred to as "a serial communication object 36," when applicable).
Further in FIG. 20, reference numeral 37 designates a keyboard controller for controlling the group of switches 223, the speed switch 221 and the reset switch 222 on the operating panel 40; 38, an input and output interface circuit for the keyboard controller; 41, an LCD controller for driving the LCD 220 in the operating panel; 42, an interface circuit for an output from the LCD controller and an input from the LCD; 44, an interruption controller which receives the output signals of the keyboard controller 37 and a feed pulse delay circuit 45 directly, and the output signal of a detector 26 through an input interface circuit 10, to cause the microcomputer 1 to provide an interruption signal; 45, the aforementioned feed pulse delay circuit for determining the timing of generation of a feed pulse with the aid of the output data of an I/0 8 and the output signal of the detector 26; 46, a floppy disk controller (hereinafter referred to as "an FDC 46," when applicable) for transmitting signals to and receiving signals from the floppy disk driver 47; 47, the aforementioned floppy disk driver for writing data in a memory medium, namely, an FD 48 in response to a signal from the FDC 46; 8, the aforementioned I/0 for controlling a variety of parallel input and output signals; 10, 11, 12, 52 and 55, input interface circuits for receiving an input signal externally provided to be applied to the I/0 8.
Further in FIG. 20, reference numeral 13 designates a power circuit for driving pulse motors in the biaxial drive section of the sewing machine (hereinafter referred to as "cloth presser drive output means or PMD," when applicable); 49, a circuit for controlling an eddy current joint type clutch motor (hereinafter referred to as "a motor control circuit," when applicable); 50, a power circuit section for operating the eddy current joint type clutch motor in response to a signal from the motor control circuit 49; 15, a switch section for changing a sewing machine control method (hereinafter referred to as "a sewing machine control method changing switch group," when applicable); 55, an interface circuit used when the I/0 8 receives signals from other than the control board; 16-a, an instantaneous power interruption detecting circuit for preventing the erroneous operation of the control board for instance when the main supply voltage is lowered temporarily; and 16-b, a power source circuit for supplying electric power to the control board.
FIG. 15 is a diagram for a description of the speed control of the conventional automatic sewing machine and one example of the actual speeds of the same. More specifically, the upper half of FIG. 15 shows speed instruction values which are applied to the motor 203 by the control circuit 50, and the lower half of FIG. 15 shows the actual speeds of rotation of the sewing machine arm shaft (not shown) with the speed instruction values. In the lower half of FIG. 15, the region A shows the fact that, although the speed instruction value is set to 2000 rpm, the actual rotation of the sewing machine arm shaft does not reach 2000 rpm; the region B shows the fact that the rotation of the sewing machine arm shaft becomes unstable because the motor is being controlled; the region C shows the fact that the rotation of the sewing machine arm shaft is stable; the region D shows the delay time in speed reduction of the sewing machine with the speed instruction value decreased to 200 rpm; and the region E shows the speed reduction time.
FIG. 16 shows two patterns of speed reduction. The upper half of FIG. 16 shows speed instruction values, and the lower half shows the speeds of the sewing machine arm shaft. The speed instruction value is 2000 rpm in the region F, 1400 rpm in the region G, 2000 rpm in the region H, and 400 rpm in the region J. On the other hand, the region K is the period in which the speed instruction value is stable, 2000 rpm; the region L is the period in which the speed of the sewing machine arm shaft is decreased with the speed instruction value decreased to 1400 rpm; the region M is the period in which the speed is being decreased; the region N is the period in which the speed is increased to 2000 rpm; the region P is the period in which the speed is held stable at 2000 rpm; the region Q is the period in which the speed of the sewing machine arm shaft is decreased when compared with the speed instruction value; and the region R is the period in which the speed is decreased to 400 rpm.
FIG. 17 shows the arrangement of the feed pulse delay circuit in detail. The detailed description of the operation of the feed pulse delay circuit will not be made here because it has been made by Published Examined Japanese Patent Application Nos. 29515/1985 and 54076/1985. That is, only the things will be described here which have not been described by these Japanese Patent Application Publications.
FIG. 18 shows the waveforms of signals in the feed pulse delay circuit shown in FIG. 17 in the case where the speed is low, 200 rpm. FIG. 19 shows the waveforms of signals in the feed pulse delay circuit in the case where the speed is high, 2000 rpm. .alpha. in FIG. 18 represents an inhibit period of time from a leading edge of a needle lower position signal DN to a leading edge of a feed pulse for driving a presser foot and .beta. in FIG. 18 represents a period of time in which the feed pulse is produced. .gamma. represents a period of time which is an interval defined by the first feed pulse and the second feed pulse. Similarly, e in FIG. 19 represents an inhibit period of time up to an occurrence of the feed pulse. In FIG. 19, .phi. represents a feed pulse production period, and .theta. represents an interval of the first and second feed pulses. As is apparent from the .gamma. in FIG. 18 and 8 in FIG. 19, even in the case of X-OUT=9 pulses, the feed pulse interval .vertline.X-OUT.vertline. differs from each other.
In the conventional automatic sewing machine thus constructed, it is impossible to set the speed of the spindle to an aimed value, and accordingly the cloth presser unit is not moved to a predetermined position (stepping out). Furthermore, the waveform of the feed pulse X-OUT changes with the speed of rotation of the sewing machine arm shaft, so that the cloth pressure unit steps out.